PROJECT SUMMARY Autoimmune posterior uveitis is an inflammatory eye disease that causes vision loss in a majority of affected individuals. Immunosuppressive treatments may reduce the inflammation, but currently available drugs act non-specifically and are associated with considerable toxicity. The overall objective of this work is to improve the clinical outcomes of patients with autoimmune posterior uveitis. Studies in experimental models have identified CD4+ T cells as initiators of the inflammation. Helper T cell subsets move from the circulation into the posterior segment of the eye across the retinal vascular endothelium. Extravasation is mediated by a specific set of endothelial adhesion molecules. There are significant differences between the human and murine immune systems. Yet, in contrast to the extensive research on this process in the mouse, there has been little consideration of the basic mechanisms operating in human disease. This project is based on the hypothesis that adhesion molecules expressed on retinal endothelial cells participate critically in the development of human posterior autoimmune uveitis and represent novel targets for therapeutic intervention. Using primary endothelial cell cultures and profiling techniques, adhesion molecules warranting further investigation were identified on human retinal endothelial cells. The impact of these molecules on migration of Th1 and Th17 cells across human retinal endothelium will be studied in adhesion and transmigration assays. Intercellular adhesion molecule 1 (ICAM-1) is strongly implicated in leukocyte extravasation in many systems, but expression is cell- and stimulus-specific. Regulation of ICAM-1 transcription in the retinal endothelial cell will be evaluated using promoter reporter expression and electrophoretic mobility shift assays. Activated leukocyte-cell adhesion molecule (ALCAM) is a novel adhesion molecule never before identified on retinal endothelium. Expression and potential functions in relation to autoimmune posterior uveitis will be investigated.